Guioa Cav.

Timothy M. A. Utteridge and Laura V. S. Jennings (2022). Trees of New Guinea. Kew Publishing. Royal Botanic Gardens, Kew

Distribution

A genus of about 65 species from South-East Asia, Malesia, Australia and the Pacific as far east as Samoa. There are 25 species in New Guinea (21 endemic).

Morphology General Habit

Trees and shrubs to 30 m tall

Morphology General Indumentum

Indumentum of simple and indistinct glandular hairs

Morphology Leaves

Leaves parpinnate, rachis winged or not, 1–9 jugate, leaflets opposite, rarely subopposite, margin entire, underside often glaucous or lighter than upper surface, papillate, domatia usually present

Morphology Reproductive morphology Inflorescences

Inflorescences axillary or terminal, thyrsoid

Morphology Reproductive morphology Flowers

Flowers unisexual or functionally so, zygomorphic, usually 5-merous; sepals imbricate, margin petaloid, outer 2 smaller than inner 3; petals clawed, with 2 marginal or ventral appendages; stamens usually 8; ovary 3-locular and 3-lobed, 1 ovule per locule, style sessile, pyramidal, with longitudinal stigmatic grooves. Fruit a 3-lobed, obcordate, loculicidal capsule, stipitate or not, lobes usually laterally flattened

Morphology Reproductive morphology Seeds

Seed testa black, aril almost covering seed, with a basal tail-like appendage.

Ecology

Guioa is sometimes found in primary forest in New Guinea, but is more common in secondary forest and also occurs in montane forest, forest edges, burned areas, roads, vine thickets, coastal and beach vegetation, Melaleuca swamp, savannahs and by rivers; from sea level to 2500 m.

Recognition

The genus can be recognised by the frequently very short petiolules (leaflets almost sessile), the upper leaf surface usually being darker than the lower, the imbricate, unequal sepals, the 3-lobed fruit, crowned by the style remnant, and the aril almost covering seed, but open at the apex and with a basal tail-like appendage.